The present invention relates to a method of producing a composite insulator comprising a core member made of for example FRP, end fitting members fixed to both end portions of the core member, and an overcoat member made of insulation material having a sheath portion formed on an outer surface of the core member and shed portions, and also relates to a packing member used for this composite insulator producing method which is arranged for preventing a flow of an overcoat forming material into a gap between the core member and the end fitting member fixed to both end portions of the core member.
Up to the present, the composite insulator comprising the core member, the end fitting members fixed to both end portions of the core member, and the overcoat member having the sheath portion formed on the core member and the shed portions is produced by various methods for example by arranging the end fitting members on both end portions of the core member, setting the core member and the end fitting members in a metal mold, filling the overcoat forming material in the metal mold, and curing the overcoat forming material. Moreover, in order to improve a seal performance between the end fitting member and the overcoat forming material, there is known a technique such that an overcoat forming material of room temperature hardening type (RTV) is used as the overcoat forming material, and also there is known a technique such that a material such as silicone gel is arranged between the end fitting member and the overcoat forming material.
Even in the method using the RTV or the method using silicone gel mentioned above, it is possible to maintain a normal seal performance, but recently more excellent seal performance is to be required. Therefore, particularly in the case of the composite insulator in which the overcoat member is made of an insulation material such as silicone rubber, there is a desire to obtain a method of producing a composite insulator in which a seal performance of a connection boundary between the end fitting member and the overcoat forming material can be maintained and an end portion of the core member can be firmly connected to an inner surface of a core member insertion hole of the end fitting member.
An object of the invention is to eliminate the drawbacks mentioned above and to provide a method of producing a composite insulator in which a seal performance of a connection boundary between a end fitting member and an overcoat member can be improved and a packing member used for this producing method.
According to the invention, a method of producing a composite insulator having a core member, end fitting members fixed to both end portions of the core member, and an overcoat member including a sheath portion formed on an outer surface of the core member and shed members, is characterized in that the overcoat member and the end fitting member are connected by curing.
According to the invention, a packing member used for the method of producing a composite insulator having a core member, end fitting members fixed to both end portions of the core member, and an overcoat member including a sheath portion formed on an outer surface of the core member and shed members, and arranged for preventing a flow of the overcoat forming material into a gap between the core member and the end fitting member fixed to an end portion of the core member, is characterized in that, if the packing member is once positioned in the end fitting member, the packing member is not moved in a direction pulling up from a position at which the packing member is positioned, when the end portion of the core member is moved in a direction pulling up from the end fitting member.
In the method of producing a composite insulator according to the invention, since a seal portion between the overcoat member and the end fitting member is constructed by curing, it is possible to improve a seal performance between the overcoat member and the end fitting member. Moreover, in the preferred embodiment, it is possible to provide a more firm curing connection between the end fitting member and the overcoat member by roughing an upper surface of the end fitting member or by subjecting a phosphate treatment to a galvanization of a surface of the end fitting member.
In the preferred embodiment of the method of producing a composite insulator according to the invention, the seal portion is cured for connection under a condition such that the end fitting member is not clamped to the end portion of the core member. In addition, the core member itself or an end portion of the core member and an inner surface of a core member insertion hole are finely worked so as to prevent a substantial flow of the overcoat forming material between an outer end surface of the core member and an inner surface of the core member insertion hole of the end fitting member when the end portion of the core member is inserted into the core member insertion hole of the end fitting member, and thus the end fitting member is fixed to the core member before forming operation or the end fitting member is preliminarily fixed to the core member before forming operation. If the overcoat forming material is flowed between an end portion of the core member and an inner surface of the core member insertion hole of the end fitting member, it is not possible to clear an specified tensile strength due to an abrasion resistance between the core member and the end fitting member.
Moreover, in the preferred embodiment of the method of producing a composite insulator according to the invention, since the seal portion defined by the overcoat member, the core member and the end fitting member is integrally formed by arranging the end fitting members to the both end portions of the core member without clamping, setting them in the metal mold, filling the overcoat forming material into an overcoat forming space between an outer surface of the core member and the metal mold, and curing under pressure so as to form the overcoat member and to connect the overcoat member to the end fitting member, or since the boundary between the end fitting member and the overcoat member is sealed by mold-forming the overcoat member around the core member, arranging the end fitting members at both end portions of the core member without clamping in such a manner that an end portion of the end fitting member is overlapped on an end portion of the overcoat member, arranging an insulation polymer material near the boundary exposed externally between the end fitting member and the overcoat member, and heating the insulation polymer material so as to cure the insulation polymer material, or since the boundary between the end fitting member and the overcoat member is sealed by mold-forming the overcoat member around the core member, arranging the end fitting members at both end portions of the core member without clamping in such a manner that a gap is existent between an end portion of the end fitting member and an end portion of the overcoat member, arranging an insulation polymer material in the gap between the end fitting member and the overcoat member, and heating the insulation polymer material so as to cure the insulation polymer material, it is possible to improve the seal performance. In addition, since a clamping operation with respect to an end portion of the core member is performed only once, it is possible to reduce an amount of producing steps of the composite insulator.
Further, in the method of producing a composite insulator comprising a core member, end fitting member fixed to both end portions of the core member, and an overcoat member having a sheath portion formed on an outer surface of the core member and shed portions, the packing member according to the invention is provided for preventing a flow of an overcoat forming material into a gap between the core member and the end fitting member fixed to an end of the core portion. If the packing member is once positioned in the end fitting member, this packing member is not moved in a direction pulling up from a position at which the packing member is positioned, when the end portion of the core member is moved in a direction pulling up from the end fitting member.
Accordingly, in the case that the composite insulator is transferred after the end fitting member is inserted into an end portion of the core member and the packing member is positioned at a predetermined portion in the end fitting member, if an end portion of the core member is moved in a direction pulling up from the end fitting member, the packing member is not moved in a direction pulling up from the position at which the packing member is preliminarily positioned in the end fitting member and is maintained at a predetermined position in the end fitting member.
Therefore, it is possible to stably seal a boundary between the core member and the end fitting member and to prevent a flow of overcoat forming material into a boundary between the core member and an inner surface of the core member insertion hole of the end fitting member. Moreover, since a metal mold is preliminarily heated and shows a thermal expansion due to a shortening of forming time and the core member maintained at room temperature is arranged in the heated metal mold, the overcoat member is formed under such a condition that an end surface of the core member is inserted into the core member insertion hole of the end fitting member with a little gap between an end surface of the core member and a bottom surface of the core member insertion hole or that an end surface of the core member is once connected to an bottom surface of the core member insertion hole and then the core member is slightly pulled up from the core member insertion hole so as to generate a little gap between an end surface of the core member and a bottom surface of the core member insertion hole. Even in the latter case, if the end fitting member is inserted into an end portion of the core member and the packing member is once positioned at a predetermined position in the end fitting member, the packing member is not moved in a direction pulling up from the position at which the packing member is once positioned and is maintained at a predetermined position in the end fitting member. Therefore, it is possible to stably seal a boundary between the core member and the end fitting member and to prevent a flow of overcoat forming material into a boundary between the core member and an inner surface of the core member insertion hole of the end fitting member.